The mechanism of renal and of neurogenic hypertension continues to represent the principal object of our studies. 1. A study of one-kidney renal hypertension in dogs (unilateral nephrectomy followed by ischemia of the contralateral kidney). The effect in such animals of inactivation of renin by antirenin, the blockade of angiotensin II by Saralasin, and the inhibition of angiotensin I-converting enzyme by SQ 20881 will be investigated. 2. The investigation of a one-kidney model of renovascular hypertension in dogs proposed by Fekete and collaborators and due to occlusion of the main artery of one kidney, followed later by the excision of the ischemic kidney. Our investigation, up to the present, has failed to confirm this work. 3. The possible abolishment of rejection of the transplanted homologous kidney of the dog by extracorporeal irradiation of the transplant, on the basis that this treatment may inactivate the lymphocytes in the transplanted kidney which are possibly involved in the immune response and the control of resistance. 4. We are participating in a study involving the acceptance of our standard unit of human renin by the College of American Pathologists for the quality control of plasma renin assays being performed in 250 American Clinical Laboratories.